1. Field of the Invention
The present invention is for a swimming event timing device, and more particularly, pertains to a capacitive relay takeoff swimming platform sensor system.
2. Description of the Prior Art
Various sensing and measuring devices and schemes have been incorporated during relay swimming events where a first relay swimmer is required to contact a touchpad sensor at the edge of a swimming pool adjacent to a second relay swimmer who then is allowed to depart in the relay sequence from a relay takeoff swimming platform (also referred to as a starting platform). Departure from the relay takeoff swimming platform is dependent on observations and timing skills of the second relay swimmer who, undesirably, may leave the starting platform prior to the touching of the touchpad sensor by the first relay swimmer. Premature departure of the second relay swimmer from the relay takeoff swimming platform can be cause for disqualification; and the International Amateur Swimming Federation (FINA) contemplates such by FINA Rule SW 10.10 which states: “In relay events, the team of a swimmer whose feet lose touch with the starting platform before the preceding teammate touches the wall shall be disqualified, unless the swimmer in default returns to the original starting point at the wall, but it shall not be necessary to return to the starting platform.” This rule pertains to relay exchanges in a relay event, and is different from the rule for the start of a race, which states that any movement before the start will disqualify the competitor. In a relay exchange, the second swimmer on the relay takeoff swimming platform can legally be completely horizontal with one toe touching the relay takeoff swimming platform when the first swimmer in the water touches the touchpad sensor on the wall.
In current practice it is difficult for an electronic timing system to detect the actual instant the second swimmer loses all contact with the relay takeoff swimming platform. Currently available relay takeoff sensors rely on measuring the force exerted by the second swimmer on the relay takeoff swimming platform, some using a mechanical switch mechanism in the relay takeoff swimming platform top, others using a pressure sensitive piezo device. Experiments have been conducted with this latter method using load cells and accelerometers. It has been demonstrated that the accuracy of force measurement methods is limited by the fact that the swimmer may have one toe in contact with the relay takeoff swimming platform, but exert an unmeasurable force against it. This results in the start being signaled before it has actually occurred. Because of this, FINA allows a tolerance of 0.03 second in relay exchange timing. In other words, a swimmer will not be disqualified unless the timing system shows a departure more than 0.03 second before the swimmer in the water touches the touchpad sensor. The “0.03 second” figure was established in tests using an Omega Sports Timing starting block, which showed that the signal from the relay takeoff swimming platform was consistently between 0.024 and 0.027 second before the actual departure.
What is needed is a system which will give an accurate measurement of the relay exchange time and which can sense contact between the second swimmer and the relay takeoff swimming platform without regard to force. Such a system is provided by the inventor by incorporating capacitive touch sensing technology. More specifically, a sensing mat, including onboard sensing circuitry, senses a capacitive field, and the change in the capacitive field generated by the second swimmer is used to derive accurate swim relay sensing and timing information within desired and approved parameters.